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Scotland and the Geologic Eye

Training students to decode 3 billion years of Earth's history

So much of becoming educated is developing an ear or an eye. Someone trained in music will impress companions at a movie by identifying the background music. And art historians are the first to suspect art forgeries because they “see” period mannerisms. The disciplinary training for many of the sciences also includes developing an eye or ear. An ornithologist can identify birds without looking upward, just by their songs. And a botanist can call out the names of various sedges, all of which look like “grass” to the rest of us.

The kings of this particular hill, however, may be field geologists. It can take years of dedicated study to develop the ‘geologic eye’ needed to read outcrops and landforms. Even Charles Darwin, who as a young man considered himself a geologist, sometimes blundered when he tried to interpret Scottish landscapes.

For those who wish to decode the riddles embedded in rocks, there is no better place to train the eye than Scotland. Perhaps nowhere else in the world are there as many geological stories crammed into as small a space.

Scotland preserves in its rocks three billion years of Earth’s history, and because it lies at a tectonic crossroads, the rocks in the region have been variously sliced, heated, stretched, and folded, creating a bewildering diversity of geological puzzles. Everything that can happen to Earth’s crust has happened here: mountain building, ocean rifting, volcanoes, tsunamis, and even meteorite impacts.

This varied, complex terrain has inspired and informed geologists for hundreds of years. Students who walk the crags and glens of Scotland today also walk in the footsteps of the men who transformed human understanding of Earth’s history, including James Hutton, who first realized that geological changes occur over time scales so vast that the human imagination, attuned to the human lifespan, has trouble comprehending them.

“It’s a small island that’s had a couple of hundred years of geologists tramping over it,” said Catherine Rose, the Steve Fossett Postdoctoral Fellow in Earth and Planetary Sciences. “There are still unsolved mysteries in Scottish geology, but many sites are well understood and clearly mapped.”

Thanks to a generous gift by H. Matsen Smith, on behalf of his wife, Marie Lange Smith (1940 alumna of earth and planetary sciences), Rose led a group of undergraduate students to Scotland this spring. Following the lead of the forefathers of modern field geology, these students sought to test and strengthen their ‘geologic eye.’

“The first day was a train wreck”

Rose earned an undergraduate degree at the University of St. Andrews, just north of Edinburgh, and has done extensive field work throughout Scotland, including an idyllic if lonely summer spent mapping the Garvellachs—small, uninhabited islands in the Inner Hebrides.

Her advisor at St. Andrews, Tony Prave, joined the group in Scotland and traveled with them. Prave co-authored Geological History of Britain and Ireland, the textbook the students studied before the trip. “Tony’s the best field geologist I’ve ever worked with,” Rose said. “One of the reasons he’s great is that he’s a brilliant observer, and that’s a real skill.”

To make sure the students would use their powers of observation and not just see what they had been told they would see, Rose didn’t show them photographs of the outcrops they would be visiting before the trip.

“We’d just show up at the site,“ says Emily Wills, a junior geochemistry major who is on the pre-med track, “and Prave would say ‘do your thing’ and we’d walk up and down the outcrop and draw it, and then come back together to talk about it.”

Wills was bitten by the geology bug when she took a course “on a whim” from Jen Smith, now dean of the College of Arts & Sciences, who also accompanied the group to Scotland. Smith’s research interest is paleoclimate, and Wills described her enthusiasm for her work as infectious.

The group began their geologic quest by looking at some of the oldest rocks on Earth: the 3-billion-year-old Lewisian gneiss that creates the knobby terrain typical of the highlands. These rocks, together with parts of Greenland and North America, were once part of the ancient continent called Laurentia.

“I remember feeling so overwhelmed,” Wills says, “and writing down anything I could possibly think of, sometimes writing about things that were completely irrelevant to the geology, like plants.”

The professors were sympathetic because they remembered their own confusion as students. “Things you observe in nature are never as pristine or obvious as the illustrations in textbooks or lectures,” said Phil Skemer, assistant professor of earth and planetary sciences and one of the faculty who accompanied the students. “And nothing prepares you for the scale of natural landscapes.”

Rose had done much the same field trip when she was about the same age as the students. “I read my old notebooks before we went,” she says. “That first day was a tough day for me as well, back then.” Like Wills, she had made careful sketches of lichens and other irrelevancies.

“The first day was a train wreck,” said Chris Thom, a junior geochemistry major. “There’s a big difference between learning in the classroom and putting it into practice in the field.”

“At first, it was really frustrating,” Wills said, “but I think I learn better by being frustrated. It makes me try harder and push myself. So I think it was the best way to learn how to do this, to be in the field.”

“The more we did, the better it got,” said Thom.

Looking into the abyss of time

One of the most memorable sites the students visited was Siccar Point, on the border between Scotland and England. Because of the role it played in the development of James Hutton’s ideas about the age of the Earth, Siccar Point is widely considered to be the most important outcrop in all of geology.

Hutton, like many members of the Scottish Enlightenment in the 18th century, was a gentleman farmer who took an interest in many different areas of science. His interest in geology formed while clearing and draining a farm he had inherited. He told a correspondent that he had “become very fond of studying the surface of the Earth, and was looking with anxious curiosity into every pit or ditch or bed of a river that fell in his way.”

Hutton traveled to different geological formations throughout Scotland in order to better understand the relationship between rock layers. At the time, there was no means of dating rocks; it wasn’t yet understood that embedded fossils could be used to tell the difference between two layers of the same type but of different ages.

“When Hutton visited Siccar Point in 1788, he realized that the rocks at the bottom would have been deposited horizontally, then tilted upright, then eroded, and then overlain with younger rocks,” said Rose, “and that every single step in this process represented a vast period of time.”

Hutton used Siccar Point and other rock formations to argue that the Earth is immensely old, far older than the few thousand years allowed by scriptural literalists.

John Playfair, a Scottish mathematician who accompanied Hutton to Siccar Point, memorably described the impact of Hutton’s bold idea: “The mind seemed to grow giddy by looking so far back into the abyss of time; and whilst we listened with earnestness and admiration to the philosopher who was now unfolding to us the order and series of these wonderful events, we became sensible how much further reason may sometimes go than imagination may venture to follow.”

Although Rose managed to keep most of the trip under wraps, hiding Siccar Point is a bit like not mentioning the Mona Lisa. For Dan Johnson, a junior majoring in environmental earth science, seeing Siccar Point was more of a spiritual experience than a learning one. Johnson traveled to Scotland in part owing to the influence of the group’s fourth faculty companion, assistant professor of earth and planetary sciences David Fike.

“Being at the place where the field of geology began was really humbling,” said Johnson,

A landscape that stumped the greatest minds of our time

Charles Darwin also took a crack at the geological puzzles of Scotland. He was particularly fascinated with the parallel “roads” in the valley of Roy (Glen Roy), which the students also visited.

In the 18th century these horizontal terraces were thought to be ancient human constructions, but by the early 19th century most visitors agreed they must be natural in origin. Still, the area had some puzzling features. Terraces appeared in adjacent valleys at slightly different levels. And the clearest ones, in Glen Roy, disappear toward the valley’s opening.

Darwin’s first substantial published paper argued for a marine origin: the terraces were the shores of ancient oceans. Soon thereafter, however, Louis Agassiz, a famous Swiss geologist, toured the highlands and, finding many traces of now-vanished ice sheets, proposed a different theory: the “roads” mark successive levels of ice-dammed glacial lakes. Like the icicle used as a murder weapon in a paperback mystery, the barriers that had impounded the lakes had melted and vanished without a trace.

Evidence that supported Agassiz’s theory soon accumulated, and Darwin eventually, and with great reluctance, abandoned his hypothesis, calling it “a great failure” and “one long gigantic blunder.”

The “roads” were a bit more of a surprise for the students than Siccar Point. The group learned that the site has a geological connection with Loch Ness, which they visited immediately before Glen Roy. When the dam that created the lowest of the “roads” burst, the water flooded into Loch Ness. “Being able to put the two together was very satisfying,” says Wills.

Acquiring a geologic eye

Acquiring a geologic eye is not easy. “To be really good at it”, says Rose, “you have to walk the extra mile and see that extra outcrop. There is no shortcut.”

“That’s why it was so important to be able to offer our students this experience,” says Skemer. “We hope that it will become a regular annual trip for our junior and senior undergraduates, to serve as an educational capstone to their time at Washington University.”

For those who, like Hutton, look with “anxious curiosity” in every pit that falls in their way, the reward is worth the effort. “It’s a cool thing to be able to walk up to an outcrop that you know nothing about and be able to use some basic geology knowledge and field methods to decode its formation and deformation,” said senior Liz Mitnick, who will graduate with a degree in environmental earth sciences.

“It was a life-changing experience,” said Johnson. “I’ll remember it fondly for the rest of my life. And it got me interested in learning more about field geology and studying earth science beyond an undergraduate degree”

- Diana Lutz is the Senior Science Editor at Washington University in St. Louis